1. Field of the Invention
This invention relates to the field of data processing systems. More particularly, this invention relates to data processing systems supporting multiple instruction sets and the way in which the registers used by those multiple instruction sets may be provided.
2. Description of the Prior Art
It is known to provide data processing systems that support multiple instruction sets. Some examples of such data processing systems are the processor designs produced by ARM Limited of Cambridge, England which support both the ARM instruction set and the Thumb instruction set. The ARM instructions are encoded in 32-bits and specify 32-bit data processing operations (e.g. ADD, SUB, LDR, STR, etc) performed upon data values held within 32-bit registers. The Thumb instructions are encoded in 16-bits and specify 32-bit data processing operations performed upon 32-bit data values stored within 32-bit registers.
The Neon and VFP architecture extensions designed by ARM Limited respectively provide SIMD and floating point instructions operating upon data values stored within registers having a size specified under program control.
It is desirable when providing a processor to reduce the amount of circuit resource required. The provision of circuit elements to form registers represents one such circuit resource.